The present invention relates to a semiconductor integrated circuit device (hereinafter referred to as an "IC"), and more particularly to aluminum interconnection lines in an IC.
With advances in integrated circuit technology, circuit element dimentions are being scaled down and interconnection lines are being made fine, so that a high integration density IC is obtainable. Such an IC has a multilevel interconnection structure, and each level interconnection line is made of a low resistivity material, i.e. aluminum, in order to suppress a signal transmission delay.
A problem occurring therein is formation of hillock which canses a short-circuit between lower and upper level aluminum interconnection lines. In order to prevent the hillock formation, it has been proposed that the surface of the aluminum interconnection line is covered with a layer of refractory metal such as titanium, molybdenum, etc.
Another problem of the aluminum interconnection line is electromigration of aluminum, which causes breaking down of fine interconnection lines.
It has been newly found that the aluminum interconnection line covered with the refractory metal layer is poor in preventing the breaking down due to the electromigration.